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PostPosted: 26 Dec 2018, 14:59 
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Joined: 25 Dec 2018, 08:41
Posts: 7
Yes I built it an it worked well.
It ran for an hour and I tried to find a hearable difference between the original and the 7812-concept
At moderate a volume, 7812 didn´t need cooling.
Adjustment of the 12v Drain-source-voltage was a little bit tricky an I had between 12 and 80mV on the speaker (8ohm).

Result: I never liked the 4700uF/10uF an so I can get rid of it. An without it I (think I )can hear more details (Best of Sade)

Next step: Better cables, better components, better speaker, PCB


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PostPosted: 27 Dec 2018, 23:13 
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Joined: 06 Jun 2008, 18:23
Posts: 5114
Location: Australia
Good to know it worked. Try a 1ohm 5W resistor in the source leg. May help to get lower offset current. I'd say about 10mV across the speaker is much better. A 10 turn pot should help fine tune it better.

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Projects:"retro2308" - chip based headphone amp | ”Calibre 834” - tube phono MM preamp | ”najah” - Raw 180W Tripath Class D power amp | "Icon" - Shuguang CV-181Z preamp


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PostPosted: 28 Dec 2018, 03:42 
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Joined: 26 Dec 2016, 03:46
Posts: 194
Location: Bayarea
It is quite dangerous to drive the speaker like this, the DC voltage ( or current ) of the MOSFET will change with temperature even in class A. Even if you trim it, when the weather change, the current through the speaker will change. If you pump too much current through the speaker, it might blow. The only safe way is to use capacitor couple to the speaker.

I cannot imagine this circuit is anything close to the word hifi. Yes, it's a single transistor amp, but for what? You might have much better luck building a chip amp. There are just too many things wrong in this circuit to even wasting time to look at, never mind building it.

One side driving is by a resistor!!! The other side by a MOSFET running in open loop !!!..............Don't even try with any decent speakers, you might blow more money than save a little money,

Want cheap and simple, look into a chip amp where everything contains in one IC.

https://www.digikey.com/products/en/integrated-circuits-ics/linear-amplifiers-audio/742?k=audio+power+amp+IC&k=&pkeyword=audio+power+amp+IC&sv=0&pv1989=0&pv183=1815&pv487=698&pv487=117&pv487=118&pv487=232&pv487=119&pv487=120&pv487=804&pv487=535&pv487=537&pv487=433&pv487=347&pv487=556&pv487=803&pv487=544&pv487=540&pv487=774&pv487=206&pv487=836&pv487=616&pv487=32&pv487=400&pv487=725&pv487=34&pv487=352&pv487=835&pv487=888&pv487=569&pv487=36&pv487=506&pv487=559&pv487=521&pv487=417&pv487=530&pv487=735&pv487=39&pv487=40&pv487=606&pv487=834&pv487=759&pv487=432&pv487=733&pv487=911&pv487=634&pv487=533&pv487=529&pv487=141&pv487=512&pv487=363&pv487=351&pv487=207&pv487=777&sf=1&FV=ffe002e6&quantity=&ColumnSort=0&page=1&stock=1&pageSize=25


Last edited by Yungman on 28 Dec 2018, 05:40, edited 1 time in total.

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PostPosted: 28 Dec 2018, 04:16 
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Joined: 23 Feb 2017, 02:02
Posts: 494
Gerti wrote:
Yes I built it an it worked well.
It ran for an hour and I tried to find a hearable difference between the original and the 7812-concept
At moderate a volume, 7812 didn´t need cooling.
Adjustment of the 12v Drain-source-voltage was a little bit tricky an I had between 12 and 80mV on the speaker (8ohm).

Result: I never liked the 4700uF/10uF an so I can get rid of it. An without it I (think I )can hear more details (Best of Sade)

Next step: Better cables, better components, better speaker, PCB


I like that, OCL like perfomance with single end schematic.
Now thats very sexy I might need to build one myself and try.

Did you know you can buy relays cheapo from aliexpress and the ones with dc voltage protection, along with a small transofmorer.
Though I'm very good with amp schematic desings I have zero exprience with relays and buying them works best for me. Cheap and fast


Last edited by ILoveHiFi on 28 Dec 2018, 04:24, edited 2 times in total.

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PostPosted: 28 Dec 2018, 04:20 
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Joined: 23 Feb 2017, 02:02
Posts: 494
Yungman wrote:
It is quite dangerous to drive the speaker like this, the DC voltage ( or current ) of the MOSFET will change with temperature even in class A. Even if you trim it, when the weather change, the current through the speaker will change. If you pump too much current through the speaker, it might blow. The only safe way is to use capacitor couple to the speaker.

I cannot imagine this circuit is anything close to the word hifi. Yes, it's a single transistor amp, but for what? You might have much better luck building a chip amp. There are just too many things wrong in this circuit to even wasting time to look at, never mind building it.

One side driving is by a resistor!!! The other side by a MOSFET with a some sort of closed loop !!!..............Don't even try with any decent speakers, you might blow more money than save a little money,

Want cheap and simple, look into a chip amp where everything contains in one IC.

https://www.digikey.com/products/en/integrated-circuits-ics/linear-amplifiers-audio/742?k=audio+power+amp+IC&k=&pkeyword=audio+power+amp+IC&sv=0&pv1989=0&pv183=1815&pv487=698&pv487=117&pv487=118&pv487=232&pv487=119&pv487=120&pv487=804&pv487=535&pv487=537&pv487=433&pv487=347&pv487=556&pv487=803&pv487=544&pv487=540&pv487=774&pv487=206&pv487=836&pv487=616&pv487=32&pv487=400&pv487=725&pv487=34&pv487=352&pv487=835&pv487=888&pv487=569&pv487=36&pv487=506&pv487=559&pv487=521&pv487=417&pv487=530&pv487=735&pv487=39&pv487=40&pv487=606&pv487=834&pv487=759&pv487=432&pv487=733&pv487=911&pv487=634&pv487=533&pv487=529&pv487=141&pv487=512&pv487=363&pv487=351&pv487=207&pv487=777&sf=1&FV=ffe002e6&quantity=&ColumnSort=0&page=1&stock=1&pageSize=25


One of the main purouses of ZCA cause its mosfet, zero feedback and simple, it sounds diffrent and unique from nfb amps.


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PostPosted: 28 Dec 2018, 04:48 
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Joined: 06 Jun 2008, 18:23
Posts: 5114
Location: Australia
I can't beleive my simple design gets so much attention. But I think my MCA sounded better and nearly as simple. Look it up on this site.

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Projects:"retro2308" - chip based headphone amp | ”Calibre 834” - tube phono MM preamp | ”najah” - Raw 180W Tripath Class D power amp | "Icon" - Shuguang CV-181Z preamp


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PostPosted: 28 Dec 2018, 05:43 
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Joined: 26 Dec 2016, 03:46
Posts: 194
Location: Bayarea
ILoveHiFi wrote:
Yungman wrote:
It is quite dangerous to drive the speaker like this, the DC voltage ( or current ) of the MOSFET will change with temperature even in class A. Even if you trim it, when the weather change, the current through the speaker will change. If you pump too much current through the speaker, it might blow. The only safe way is to use capacitor couple to the speaker.

I cannot imagine this circuit is anything close to the word hifi. Yes, it's a single transistor amp, but for what? You might have much better luck building a chip amp. There are just too many things wrong in this circuit to even wasting time to look at, never mind building it.

One side driving is by a resistor!!! The other side by a MOSFET with a some sort of closed loop !!!..............Don't even try with any decent speakers, you might blow more money than save a little money,

Want cheap and simple, look into a chip amp where everything contains in one IC.

https://www.digikey.com/products/en/integrated-circuits-ics/linear-amplifiers-audio/742?k=audio+power+amp+IC&k=&pkeyword=audio+power+amp+IC&sv=0&pv1989=0&pv183=1815&pv487=698&pv487=117&pv487=118&pv487=232&pv487=119&pv487=120&pv487=804&pv487=535&pv487=537&pv487=433&pv487=347&pv487=556&pv487=803&pv487=544&pv487=540&pv487=774&pv487=206&pv487=836&pv487=616&pv487=32&pv487=400&pv487=725&pv487=34&pv487=352&pv487=835&pv487=888&pv487=569&pv487=36&pv487=506&pv487=559&pv487=521&pv487=417&pv487=530&pv487=735&pv487=39&pv487=40&pv487=606&pv487=834&pv487=759&pv487=432&pv487=733&pv487=911&pv487=634&pv487=533&pv487=529&pv487=141&pv487=512&pv487=363&pv487=351&pv487=207&pv487=777&sf=1&FV=ffe002e6&quantity=&ColumnSort=0&page=1&stock=1&pageSize=25


One of the main purouses of ZCA cause its mosfet, zero feedback and simple, it sounds diffrent and unique from nfb amps.

The cost is on the power transformer and filter caps, not just save on transistors. It's effort to build the amp.

Different sound in what way? Good way or bad way? I cannot imagine it's in good way. And super low power.


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PostPosted: 28 Dec 2018, 09:44 
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Joined: 25 Dec 2018, 08:41
Posts: 7
@ Yungman: See a pic from my last project: chips and 2x200W/8R.

What´s it all about for me?
The erotic of actually only 6 components (+PS) making surprisingly good music at ~1W fed by USB-DAC
True is: The temperature behaviour of the FET has to be monitored. (A job for a multimeter with USB and EXCEL)
And if the DC ripple of the PS is acceptable, the 78/79s are out and the money goes to: more filter caps


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PostPosted: 31 Dec 2018, 05:31 
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Joined: 23 Feb 2017, 02:02
Posts: 494
From exprience with zero negative feedback amps which zca falls into this list, my zero nfb ocl amp yeilds very high frequency response and gain bandwith, if done well sound can be unique awesome simple low distortion and base sound quality is very hard to beat.


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 Post subject: ZCA project completed !
PostPosted: 09 Mar 2019, 18:01 
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Joined: 25 Dec 2018, 08:41
Posts: 7
The project was completed.
Including some photos:





Thank you all for your comments and inspiration

Gerti


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